Can you explain how a non-uniform airgap reduces cogging?
And if it does, flat magnets should do the trick too? Because then the distance in the middle of the magnet to the stator would be bigger than at the sides of the magnet, basically an 'inside-out' situation from what's pictured above.
I like the idea of the stainless steel band to secure magnets in place.
What it is? Isn't that obvious? How many '403's are there. And what's this board all about? Duh... 
To the original poster: you can't have enough pictures (some people (like me) have never seen a 403 for real). The more pictures, the better. Of the prop, mounting, pivot/yawing arrangement, etc.etc.
The overtemperature safeties have me puzzled a bit too... When the stator gets too hot it disconnects, causing runaway of the prop, I'd think.
Peter.